Thermodynamics of a nonionic sponge phase

Different suggestions for the mechanism governing the narrow stability of the L-3 (sponge) phase have led to a series of debates in recent years. There have been several models developed to describe such a mechanism via thermodynamics. To date, experimental data are insufficient to test present theories. In this study, we revisit the-sponge phase with two series of thermodynamic data performed on the well-characterized C12E5-n-decane-H2O system. These thermodynamic data sets stem from phase equilibrium and static light scattering experiments designed to link system-specific parameters such as the temperature dependence of the spontaneous curvature H-o, and the two bending moduli kappa and <(kappa)over bar>, which have only been loosely connected in earlier experiments. The use of a well-characterized system is important in that it allows usage elf molecular descriptors from earlier studies to reduce fit parameters. Another advantage for using this system is that its phase behavior is analogous to a two-component system which, from an experimental standpoint, is more practical. to perform accurate measurements and, from a theoretical standpoint, more simple to model. In the present investigation, we use these tools to quantitatively test parameters obtained by different experimental techniques and assumptions inherited in theoretical models designed to interpret them. [S1063-651X(99)02210-2].